The development of stimuli responsive films and surfaces has been explored and studied for many applications including tissue engineering (1, 2), permeable membranes (3), and packaging materials (4). These materials usually undergo some significant change in their physical properties due to a global stimulus, such as temperature, pH, or light.
By carefully choosing the additive, one can selectively manipulate specific physical properties including impact strength, magnetic, electronic, and optical properties, and conductivity.
Through deliberate materials design and engineering, these changes in physical properties can be used to engineer a specific response to a specific trigger, allowing the design of devices or systems which respond in a useful manner to changes in their environments, without monitoring or activation.
For example, by controlling the composition and molecular weight of core@shell polymer nanoparticles, one can manipulate processing parameters for thermoplastic elastomers (5). Controlling the addition and dispersion of CaCO3, nanoparticles within PMMA matrices results in abrasion resistant polymer coatings (6). Alumina and silica particles have commonly been utilized to manipulate tensile strength, glass transition temperatures, and impact strength (7-10). Additionally, various computer simulations have been employed to predict not only additive location, but the potential impact upon physical property characteristics (11-14).
A wide range of techniques have been utilized to study and prepare phase segregated polymer surfaces (5-17). Koberstein et al. have prepared a variety of systems showing microphase separation of block copolymers, driven by the immiscibility of the component blocks and focusing on the effects of variations in polymer architecture and composition (28, 29). Koberstein et al. demonstrated the mobilization, also referred to as “blooming”, of chain-end fluorinated polystyrene (PS) to the surface of a poly(dimethylsiloxane) (PDMS) spin-coated film. It was found that the key driving force for blooming is the reduction of surface energy. This approach has met with limited acceptance owing to the blooming of molecules occurring immediately upon processing; rather it is desirable to control the timing of phase composition modification.
Kramer et al. have shown that the location of gold nanoparticles in a PS-b-poly(2-vinyl pyridine) (PS-b-P2VP) copolymer is controlled by adjusting the ligand composition from 100% PS to a 1:1 molar mixture of PS and P2VP ligands or by decreasing amounts of only PS-ligand used, which results in the equilibrium location of the gold nanoparticles from the center of the PS domains to the interface between microphase separated PS and P2VP lamellae (30, 31). Again, the location of the nanoparticle is determined a priori by ligand composition and coverage, which affect particle size, particle miscibility, and the adsorption energy of the particle at the interface between microphase separated domains.
Thus, there exists a need for a broadly applicable composition capable of migration within a polymer in response to a thermal stimulus matrix. Additionally, there exists a need for a composition capable of self-segregating to a polymeric matrix surface or migrating relative to other molecules of the composition in concert with a macromolecule particle to further modify the matrix surface without resorting to the application of subsequently applied coating.